Croaking science is a new way for students, volunteers and scientists to explore what’s occurring in the world of Science – science facts, new research or old debates which are inspired by or affect amphibians and reptiles, and then communicate this to a wider audience in their own words. The aim of the feature is to provide a platform for those starting their foray into the world of science communications as well as established scientists. We welcome any submissions from students and scientists. Please note that the views expressed in the articles are not those of the Froglife Trust.
Our Croaking Science reporter Gemma Rate finds out what some of our species do when winter comes.
Though there doesn’t seem to be much snow in the UK at the moment, north of the Arctic Circle, it’s a different story. The only amphibian species which makes its home in this harsh climate is the wood frog Rana (Lithobates) sylvatica. Typically found in North America, wood frogs can live in Tundra, wet grasslands and woodlands, usually making use of rain pools and snowmelt for breeding. They are physically adapted for the cold, and remain frozen during their winter hibernation, surviving temperature dips to -6°C. Ice crystals can severely damage cells by drawing out the water inside; wood frogs get around this problem by producing large quantities of glucose. This prevents ice from freezing the cell interiors, and also stops dehydration, by locking in the water molecules. They also have proteins in their blood which regulates ice crystal formation. The frog’s heart and blood flow stop during this time, though they restart again during thawing.
Interestingly, wood frog eggs are also adapted to the Arctic conditions; when the surrounding jelly freezes, it dehydrates the central egg. This helps the egg to survive the extreme temperature changes during the spring.
Like our own species, these intrepid cold frontier species are under pressure from human activities. The loss of terrestrial and aquatic habitats through deforestation, increased agricultural land use and fragmentation via road building, have resulted in declines in wood frog numbers. In addition, air pollution including acid rain can have negative effects on all growth stages of this species.
What you can do to help:
Our species can need a little bit of help to survive the winter if they don’t have access to suitable hibernation sites. Why not make your own shelter for amphibians in your garden and find out other ways of improving your garden for both your enjoyment and theirs.
If you are a farmer looking for more advice on improving your land for different wildlife species, free information is available on our land management page.
AmphibiaWeb (2014). Rana sylvatica: wood frogs. Berkeley, California. http://amphibiaweb.org/. (Accessed: 03/01/2013).
S.O Macdonald. Wood frog. Amphibians and Reptiles of Alaska: a field hand book, (last retrieved 3/1/2014),
The Pennsylvania State University (2002). The Virtual Nature Trail at Penn State New Kensington: species page. (last retrieved 3/1/2014),